With the Joyn card or app, customers can save points and redeem rewards or coupons in participating businesses. The first chart on the stats page shows the scanning behaviour in your business. This provides a good idea of your business' peak and off-peak hours. But it also shows you which coupons work well, and which ones don't.
One of the things your stats tell you is how many customers have scanned in your business at least once. You dispose of detailed information about all these customers, meaning you can send them targeted promotions. Personal details such as age, gender and place of residence give you a good idea of your customer base. And they indicate whether or not you're reaching the target audience you want to reach. The more customers register, the more accurate your data will be.
So you have every reason to encourage your customers to register. If they're using the app, they'll have to register at some point. If they're using the card, you are co-responsible for filling out their details. The more details they enter, the more return you'll have!